wonderland will stay at north america through january 4. children four years and under get in for free. >>> a lot of fresh new snow in the sierra tonight and an incredible example of human nature. a chain installers mission to return a lost wedding ring. >> chilling new details in the case of a fire. >>> at first, firefighters report of an an explosion in downtown san francisco. what they found on the scene. >>> a manhole cover exploded in downtown san francisco this evening. pg & e says it was caused by an underground vault fire. the blast happened around 5:00 this evening near the corner of third and mission street. the intersection was closed to traffic for a while as crews put out the fire. no one was injured and there was no power outages. >>> investigators have found a note and human remains at the home of a man who's accused of deliberately setting a fire and then shooting and killing two firefighters that arrived at the scene. david lee miller has the new details emerging on the man at the center of this attack. >> reporter: when fi